There is a critical and ever-growing need for metallic materials with significantly enhanced properties, such as yield and ultimate strength, fracture toughness, fatigue strength, resistance to tribological and environmentally-assisted damage, machinability, formability and joinability, when compared to current state of the art metallic materials. The goal is to improve cost, delivery and reliability of components in commercial and military aircraft, satellites, weapons, electronic and defense systems, spacecraft and launch systems.
For example, the cost of fuel is a significant economic factor in the operation of commercial vehicles, such as passenger aircraft and cargo aircraft. Therefore, aircraft designers and manufacturers continue to seek methods to improve the overall fuel efficiency of aircraft and, thus, reduce overall aircraft operating expenses. One well-established technique for increasing fuel efficiency, as well as enhancing overall aircraft performance, is reducing the structural weight of the aircraft. This is accomplished by designing various structural components of an aircraft using materials with high strength-to-weight ratio, such as aluminum, titanium and magnesium alloys, thereby reducing the overall structural weight of the aircraft and, thus, increasing fuel economy.
Nanocrystalline (NC) and ultrafine grained (UFG) metallic materials have shown promise of meeting the aforementioned goals for enhanced performance. They are routinely being synthesized at laboratory scale and major advancements have been made in understanding their behavior. However, excitement brought about by the potential of bulk NC/UFG metallic materials, especially as a result of their very high strength, has been tempered by their disappointingly low ductility and toughness, limiting most engineering applications of NC/UFG metallic materials. Additionally, commercial application of NC/UFG metallic materials beyond laboratory boundaries depends strongly on the successful consolidation and/or thermomechanical processing of these materials into bulk components while preserving their nanocrystalline and/or ultra fine grain size. Grain growth, which is a result of the poor thermal stability of NC/UFG metallic materials, severely limits such critical processing steps.
Accordingly, those skilled in the art continue with research and development efforts in the field of metallic material production and, particularly, production of performance enhanced metallic materials.